Windshield wiper drive mechanism



Jan. 16, 1962 E. R ZIEGLER 3,015,753

WINDSHIELD WIPER DRIVE MECHANISM Filed Nov. 10, 1958 3 Sheets-Sheet lINVENTOR. [UGHIE R. Z/fGlfR H15 ATTORNH Jan. 16, 1962 E. R. ZIEGLER3,016,753

WINDSHIELD WIPER DRIVE MECHANISM Filed Nov. 10, 1958 3 Sheets-Sheet 2 INV EN TOR.

EUGENE R. z/mm W W H/s ATTORNEY Jan. 16, 1962 E. R. ZIEGLER WINDSHIELDWIPER DRIVE MECHANISM 3 Sheets-Sheet 3 Filed Nov. 10, i958 IN V EN TOR.EUGENE B. Z/[GLER Hi5 ATTORNEY Patented Jan, 16, 1962 3,tlld,753WlNDSlllElsD ii/HPER DREVE MECHANlSM Eugc ie it. Zie ler, Spcncerpcrt,NE! assiguor to Gen and Motors Qorporatlon, Detroit, Mich, a corporationof Delaware Filed Nov. til, 195d, 5812. No. 772,888 3 Claims, (Cl. 7495)This invention pertains to the art of windshield cleaning, andparticularly to an improved drive mechanism for windshield wipers.

In my prior application Serial No. 726,931, filed April 7, 1958, and nowPatent No. 2,947,185, a linkage drive for windshield wipers is disclosedwherein the angular velocity at the stroke ends of the wipertransmission shafts is automatically reduced to prevent overtravel. Thepresent invention relates to a simplified drive mechanism of theaforesaid type which is adaptable to either a single or a doublerotating crank driving member. Accordingly, among my objects are theprovision of a linkage drive for converting rotation to oscillationincluding eccentric means for automatically reducing the angularvelocity of a wiper transmission shaft adjacent the stroke ends thereof;the further provision of a wiper drive linkage including a flexiblemetal strip which is maintained under tension at all times; and thestill further provision of a windshield wiper transmission assemblyincluding a shaft, an eccentric, and torsion spring means for biasingthe shaft in one direction.

The aforementioned and other objects are accomplished in the presentinvention by attaching an eccentric to a wiper shaft and biasin theeccentric and shaft assembly in one direction by means of a torsionspring. Specifically, two embodiments of an improved wiper drive linkageare disclosed herein, both embodiments being driven by rotary crankmeans. During normal running operation the crank means rotates about afixed axis, and to obtain depressed gnarl j the axis of the crank meanscan be shifted to vary the throw thereof. The mechanism for shifting theaxis of the crank means may be of the type disclosed in copendingapplication Serial No. 718,789 filed March 3, i958, and now Patent No.2,985,024, in the name of Contant et a1. and assigned to the assignee ofthis invention.

in one embodiment, a single rotating crank is employed in combinationwith a pair of flexible metal strips. The inner ends of the strips arerotatably connected to the crank arm, and in order to obtainasymmetrical oscillation of the spaced wiper transmission shafts, one ofthe strips extends above the transmission shaft and the other stripextends below the transmission shaft. Each transmission shaft isrotatably journallecl in a housing, or bracket, fixedly secured to thevehicle. An eccentric drum member is fixedly secured to the inner end ofeach transmission shaft, the axis of each shaft being disposed betweenthe periphery of the eccentric and the center thereof whereby thedistance between the axis of the wiper shaft and the periphery of theeccentric, or the moment arm, is shortest at the center of the wipingstroke and is longest at the stroke ends. Each transmission assemblyalso includes a torsion spring mounted coaxially with the transmissionshaft, one end of which engages the mounting bracket, and the other endof which engages the eccentric for biasing its respective eccentric andtransmission shaft towards one stroke end position. Accordingly, theflexible metal strips are maintained under tension at all times, andupon rotation of the single crank arm oscillation will be imparted tothe wiper blades and arms attached to the spaced transmission shafts.

In the second embodiment the crank means comprises a double crank, andaccordingly, the linkage drive from the double crank means to thetransmission can be located beneath the pivot shafts. In this embodimentthe linkage drive to one transmission comprises a flexible metal strip,while the drive to the other transmission comprises a rigid link and aflexible strip interconnecting the outer end of the rigid link and theeccentric of the other transmission. in both embodiments the torsionspring torques balance out each other at the rotating drive crank meanssince they tend to rotate the drive crank means in opposite directions.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being ad to the accompanyingdrawings, wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a fragmentary view, in elevation, of a motor vehicle withcertain parts broken away, equipped with the windshield wiper drivemechanism of this invention.

FIGURE 2 is an enlarged fragmentary sectional view of the improvedwindshield wiper transmission assembly taken along line 22 of FIGURE 1.

FIGURE 3 is a fragmentary top View illustrating a linkage driveconstructed according to one embodiment of this invention.

FIGURE 4 is a View taken in the direction of arrow 4- of FIGURE 3.

FIGURE 5 is a fragmentary top view of a wiper drive linkage constructedaccording to the second embodiment of this invention.

FIGURE 6 is a fragmentary view taken in the direction of arrow 6 ofFIGURE 5.

With reference to FIGURE 1, a portion of a vehicle is shown illustratinga windshield it), the outer surface of which is adapted to be cleaned bya pair of wiper blades 12 and 14 carried by oscillatory arms 15 and 13which are drivingly connected with spaced transmission, or pivot shafts,2d and 22, respectively. The wiper blades 12 and 1d are oscillatedasymmetrically throughout wiping strokes A and can be moved to adepressed parked position throughout the angle B.

With reference to FIGURE 2, each of the transmission shafts 2d and 22are rotatably journalled in a bearing bracket 2% rigidly attached to thevehicle, by any suitable means, not shown. Since the transmissionassemblies are identical, only one will be described in detail, likeparts of the other being indicated by like numerals with primes aflixed.An eccentric drum member 26 is rigidly attached to the inner end of thepivot shaft, and the pivot shaft is encircled by a torsion spring 28.One end 30 of the torsion spring is connected to its respectiveeccentric, and the other end 32 of the torsion spring is attached to itsbearing bracket. The torsion springs are wound so that they normallybias the wiper arms and blades towards opposite stroke end positions.

With reference to FIGURES 3 and 4, in the first embodiment, theeccentrics 2t: and 26 for the drivers and passengers sides of thevehicle have arcuate peripheries, the centers of which are indicated bynumerals 34 and 34, respectively. Accordingly, it is apparent that theaxes of the pivot shafts 2t and 22 are disposed between the periphery ofthe eccentrics and the centers thereof. In the embodiment of FIGURES 1through 4, the wiper arms and blades are driven from a suitably rotarymotor 36 having a vertically disposed rotary output shaft 38. The outputshaft 38 has a single crank arm at} extending therefrom, and the axis ofthe shaft 38 can be shifted from the full to the dotted line position asshown in FIGURE 3 to achieve depressed parking.

Since in the embodiment of FlGURES 1 and 4 the rotary driving motor hasonly a single crank arm, in order to obtain asymmetrical oscillation ofthe spaced wiper arms and blades, the eccentric 26' connected to thepivot shaft on the passengers side of the vehicle is inverted withrespect to the eccentric 26 on the drivers side of the vehicle. A pairof flexible steel strips 42 and 44 having their inner ends rotatablyconnected to the crank arm 40, or more particularly to the crank pin 46adjacent the outer end of the crank arm 41 and their outer endsconnected by means of fasteners 48 and 50 to the eccentrics 26 and 26,are utilized to convert rotation of the crank 40 to oscillation of thepivot shafts 2t and 22. As aforementioned, the torsion springs 28 and28' inherently bias the pivot shafts 20 and 22 towards opposite strokeend positions. In other words, the torsion springs tend to rotate theirrespective eccentrics in the counterclockwisedirection as viewed inFIGURE 4, whereby the flexible steel strips 42 and 44 will be maintainedunder tension at all times. Due to the fact that the torsion springloads oppose each other in tending to rotate the crank 40 in oppositedirections, the spring torques balance out each other. Accordingly,during rotation of the crank as, the flexible metal strips 42 and 44will alternately be placed under tension by rotation of the crank and bytheir respective torsion springs. Moreover, due to the fact that themoment arms of the eccentrics increase adjacent the stroke ends of thewiper blades, the angular velocity of the pivot shafts, and hence thewiper arms and blades adjacent the stroke end will be a minimum whereasthe angular velocity will be a maximum substantially midwaytherebetween.

With reference to FIGURES and 6, in the second embodiment the Wipermotor driven shaft 38 has a double crank arm 49 attached thereto, eachend of which carries a crank pin 51 and 52, respectively. The crank pin51 is connected with the drivers wiper transmission including eccentric26 and flexible steel band 42. Since in the embodiment of FIGURES 5 and6 a double crank arm 49 is employed, the eccentrics associated with thepivot shafts on the drivers and passengers sides of the vehicle can havethe same relationship. However, in order to actuate the passengerstransmission, a rigid link, in the form of a tube 54, is rotatablyconnected at one end to the crank pin 52 and is rigidly connected bymeans of a fastener 56 to the end of a flexible steel strip 58 adjacentthe eccentric 26. The other end of the flexib'e steel strip 58 isattached to the eccentric 26 by a fastener 50.

In the embodiment of FIGURES 5 and 6, the torsion spring 28 biases thepivot shaft 20 towards the outboard stroke end whereas the torsionspring 28 biases the pivot shaft 22 towards the inboard stroke end.Accordingly, the spring torques balance out each other, since thetorsion spring 28' exerts a compression load on the rigid link 54 andthe torsion spring 23 exerts a tension load on the flexible metal strip42. However, since the crank arm 49 is double ended the torque of spring28 tends to rotate crank arm 49 in the counterclockwise directionwhereas the torque of spring 28 tends to rotate the crank arm 49 in theclockwise direction. Therefore, upon rotation of the shaft 38 and thecrank arm 49, asymmetrical oscillation will be imparted to the spacedWiper shafts and blades and carried thereby, and the flexible metalstrips will be maintained under tension at all times.

While the embodiments of the invention as herein disclosed constitutepreferred forms, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. A windshield wiper drive including in combination, unidirectionalrotary crank means, a pair of spaced pivot shafts rotatably supported byspaced brackets, an eccentric drum member attached to each pivot shafthaving an arcuate peripheral surface, the axis of each shaft beingdisposed between the arcuate peripheral surface and the center thereofwhereby the angular velocity of each shaft will be a maximum at itsmid-stroke position and a minimum at its stroke end position, a torsionspring operatively associated with each pivot shaft, said torsionsprings biasing said pivot shafts in the same rotary direction, andmeans operatively interconnecting said'crank means and said drum membersso as to effect angular movement of said pivot shafts in oppositedirections during rotation of said crank means, said means including apair of flexible strips, each flexible strip having one end operativelyconnected with said crank means and its other end secured to one of saiddrum members such that during each half revolution of said crank meansone of said strips is unwound from its drum member and the torsionspring associated with its shaft is stressed, while the other strip iswound on its drum member by the spring associated with its shaft wherebysaid flexible strips are maintained under tension at all times and thetorques created by said torsion springs offset each other.

2. The windshield wiper drives set forth in claim 1 wherein said rotarycrank means comprises a single ended crank, and wherein one end of eachflexible strip is movably connected to said single ended crank.

3. The windshield Wiper drive set forth in claim 1 wherein the rotarycrank means comprises a double ended crank, one of said flexible stripsbeing movably connected to one end of said double ended crank and theother of said flexible strips being operatively connected to the therend of said double ended crank through a rigid link.

References Cited in the file of this patent UNITED STATES PATENTS328,678 Hogsett Oct. 20, 1895 562,124 Doolittle June 16, 1896 2,172,488Waters Sept. 12, 1939 2,790,333 Dyer Apr. 30, 1957 2,856,901 Kvarnstromet al Oct. 21, 1958 2,901,764 Anderson Sept. 1, 1959

